Museum search finds an 86.6 mm Tennessee bottlebrush crayfish bigger than Crawzilla
Illinois biologist Caitlin Bloomer's nationwide search found an 86.6 mm Tennessee bottlebrush crayfish, the largest specimen it identified. The measurements hint at a common size ceiling, with muscle or shell limits offered as a possible cause.
The Scientist · Science desk
Share bars: the Illinois Natural History Survey accounted for 6 of the 20 largest crayfish; the Smithsonian's National Museum of Natural History contributed 4 of the 20; together the two institutions supplied 10 of the 20, half the list.
- Both institutions together, claim 12 10 of 20 crayfish 50% computed
Both institutions together The rest of the 20
- Illinois Natural History Survey, claim 11 6 of 20 crayfish 30% computed
Illinois Natural History Survey The rest of the 20
- Smithsonian Nat. History Museum, claim 11 4 of 20 crayfish 20% computed
Smithsonian Nat. History Museum The rest of the 20
| Share | Part | Whole | Percent | Claim |
|---|---|---|---|---|
| Both institutions together | 10 crayfish | 20 crayfish | 50% (computed) | 12 |
| Illinois Natural History Survey | 6 crayfish | 20 crayfish | 30% (computed) | 11 |
| Smithsonian Nat. History Museum | 4 crayfish | 20 crayfish | 20% (computed) | 11 |
What happened
- Bloomer contacted biologists and museum curators across the country and asked them to examine their collections for unusually large crayfish.
- The search produced a list of 20 exceptionally large individuals from 18 species, and the results were published in the journal Ecology.
- The record-holder was collected in 2011 by Zac Loughman and West Liberty University students, so the find came from an existing museum specimen.
Why it matters
- What it limits constraint Until full size distributions are published, the ceiling describes 20 selected animals and cannot stand as a limit for any single species.
- What's now possible capability Preserved collections can answer size-limit questions without new fieldwork, since the largest animal had been sitting in a collection for years.
- Who's exposed exposure With half the list coming from two institutions, the record holds only for the collections searched, and an unsearched jar could hold a bigger animal.
The researchers compared preserved crayfish with calipers [3], and the 86.6 mm figure leaves out the tail, claws and antennae [7]. Zackary Graham, an assistant professor of biology at West Liberty University, said: "Its carapace alone is about the length of a credit card, and with the tail and claws, it stretches nearly the width of a sheet of notebook paper." [10] Tennessee bottlebrush crayfish is the species name. The animal itself sits in West Liberty's collection in West Virginia [7].
The 20 on the list are the largest animals that biologists and curators turned up when asked to look through their collections [2]. That is a selected set. The list covers 18 species, so only two animals sit beyond one per species, and at least 16 species are represented by a single specimen [13]. The thing this doesn't tell you is how many crayfish were examined to produce the 20. The source summary does not report a total.
From these measurements the researchers drew some of the first estimates of upper size limits for North American crayfish [14]. Despite differences among species and environments, the largest individuals tended to reach roughly the same size, and the results suggested a consistent growth ceiling [15]. Muscles or protective shells are the possible cause [16]. We think the ceiling is a fair description of these 20 animals. A tight cluster near the top is also what a modest sample from a thin upper tail would produce, so a summary of the top 20 cannot tell the two apart.
Two institutions supplied half the list. The Illinois Natural History Survey, part of the Prairie Research Institute at the University of Illinois, accounted for six of the 20 and the Smithsonian's National Museum of Natural History for four [11], ten in all [12]. West Liberty holds the top two. Graham said: "I knew we had some massive crayfish in the West Liberty University Astacology Collection, but it was a surprise to learn we had the two largest specimens known from North America!" [9]
Crawzilla, the Kentucky catch that started the search [1], came in lower. Bloomer said: "Mine was not the biggest, but it did make the top 20, so I'm super proud of it." [5] She added: "And it was also the only burrowing crayfish to make the list, so I'll take the win." [6]
What to watch
- Whether other museum collections report a North American crayfish larger than 86.6 mm.
- Whether anyone measures muscle or shell in the largest crayfish to test the possible cause of the ceiling.
- Whether the Ecology paper's full size data, species by species, show the same cluster near the top.
Clarity's read
What the record supports and how the coverage leans. The claims behind it follow.
Reality
- Evidence55
- Adoption
- Not scored
- Hype gap+15
- Incentives
- Not scored
- Confidence50
Claim ledger
Ranked by verification strength, evidence, and original report placement.
- [1]
Caitlin Bloomer pulled an enormous Crawzilla crawdad from the mud during a biological survey in Kentucky, which began the investigation.
- [2]
Bloomer contacted biologists and museum curators across the country and asked them to examine their collections for unusually large specimens.
- [3]
The researchers used calipers to compare the sizes of preserved crayfish.
- [4]
The search produced a list of 20 exceptionally large individuals representing 18 different species, and the results were published in the journal Ecology.
- [5]
"Mine was not the biggest, but it did make the top 20, so I'm super proud of it," Bloomer said.
- [6]
"And it was also the only burrowing crayfish to make the list, so I'll take the win," Bloomer said.
- [7]
The biggest specimen was a Tennessee bottlebrush crayfish preserved in the collection at West Liberty University in West Virginia; it measured 86.6 millimeters, about 3.4 inches, excluding its tail, claws and antennae.
- [8]
The record-holder was collected in 2011 by Dr. Zac Loughman and students from West Liberty University, so the discovery came from examining existing museum specimens.
- [9]
"I knew we had some massive crayfish in the West Liberty University Astacology Collection, but it was a surprise to learn we had the two largest specimens known from North America!" said Graham.
- [10]
"Its carapace alone is about the length of a credit card, and with the tail and claws, it stretches nearly the width of a sheet of notebook paper," said Graham.
- [11]
The Illinois Natural History Survey, which belongs to the Prairie Research Institute at the University of Illinois, accounted for six of the 20 largest crayfish, and the Smithsonian Institution's National Museum of Natural History contributed another four.
- [12]
Two institutions together supplied ten of the 20 largest crayfish, half the list.
- [13]
With 20 individuals across 18 species there are only 2 animals beyond one per species, so at least 16 species are represented by a single specimen.
- [14]
The researchers' measurements provided some of the first estimates of the upper size limits for North American crayfish.
- [15]
Despite differences among species and environments, the largest individuals tended to reach roughly the same size, and the results suggested these animals may face a surprisingly consistent growth ceiling.
- [16]
The scientists suggest North American crayfish seem to hit a biological size limit, possibly because of their muscles or protective shells.
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Sources
1 independent publisher whose own reporting we read for this story.
- sciencedaily.com“Crawzilla” was huge. Then scientists found an even bigger crayfish
1 article · October 15, 2026
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